|Publication number||US7297879 B2|
|Application number||US 11/129,019|
|Publication date||Nov 20, 2007|
|Filing date||May 13, 2005|
|Priority date||Dec 27, 1994|
|Also published as||US6940025, US20050205307|
|Publication number||11129019, 129019, US 7297879 B2, US 7297879B2, US-B2-7297879, US7297879 B2, US7297879B2|
|Inventors||James A. Salomon|
|Original Assignee||Pitney Bowes Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (15), Referenced by (14), Classifications (10), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a continuation of U.S. patent application Ser. No. 08/364,144 filed Dec. 27, 1994, now U.S. Pat. No. 6,940,025 and assigned to the assignee of the present invention. This application is specifically incorporated herein in its entirety by reference.
The subject invention relates to a method for rapidly determining the mass of a mail piece.
Mailing systems where a mail piece is transported onto a postal scale, the appropriate postage is determined and used to set a postage meter, and the mail piece is then transported to the postage meter for imprinting with a postal indicia representative of the postage amount are known. One such system is described in U.S. Pat. No. 4,742,878, issued May 10, 1988 to the assignee of the subject invention. In such systems, there is a constant need to increase the rate at which the scale can determine the mass of a mail piece in order that the throughput of the system can be increased. Heretofore, weighing devices for such mail processing systems have been developed, but these generally have been rather slow. Actually, many prior weight devices combined a standard scale with a mechanism that would stop the mail to allow weighing to take place. These systems require large transports and high acceleration and deceleration rates. To keep pace with a high throughout rate, multiple scales would be used with alternate mail pieces diverted to such scales.
A separate approach for providing high throughput mailing systems has been the use of vibrating tray scales to determine the mass of a mail piece where the mass is estimated as a function of the frequency at which a scale tray vibrates after a mail piece is placed upon it and the system is excited. Such a system is described in U.S. Pat. No. 5,082,072. While such prior art systems have proven generally satisfactory, there is still a need for a method of operation which is suitable for use with load cell technology while still providing desired high throughput rates of at least three mail pieces per second for mailing systems.
It is therefore an object of the present invention to provide a method for determining the mass of an article in motion. For the purpose of determining the mass of the article, a platform and an associated means for transporting the article are mounted on resilient support means. A load cell is oriented in such a manner as to measure a horizontal force applied to the load cell by the transported article. The transporting means moves the article across the platform, without stopping, in accordance with a known acceleration profile. While the article is in motion, a load cell measures the horizontal force acting on the load cell. The horizontal force is then correlated with the acceleration rate of the article in order to determine the mass of the article.
In another embodiment of the invention, a multiple frequency, time varying velocity profile is applied to a servo motor which controls the motion of the article. The current output of the motor passes through a current limiter. Predetermined weight breaks are identified by predetermining which frequency will saturate the current limiter for an article of a known mass. For each frequency, with the transported article on the platform, the output of the current limiter is measured. By comparing the frequency of the velocity signal when the motor is current limited against the predetermined frequencies which saturate the current limiter, the mass of the article is rapidly determined.
These and other objects and advantages of the present invention will become apparent from the following description of the accompanying drawings. It is to be understood that the drawings are to be used for the purpose of illustration only, and not as a definition of the invention. In the drawings:
With reference to
On the downstream side of the weighing conveyer 1 is the metering module 20 for imprinting a mail piece 13 with an indicia. With reference to
Data from the load cell 2 is subject to errors from several sources, including external vibrations and electronic noise. Hence, the digital signals are processed by digital filter 106. Preferably such a filter would be a Kalman filter which may be implemented in a known manner in any of a number of commercially available microprocessors specially adapted for digital signal processing. The Kalman filter can factor into account the error sources and provide a filtered signal of the current mass of the mail piece 13 seen by the load cell 2. The filter 106 may eliminate high frequency electrical noise and low frequency mechanical noise from the signal received from the load cell 2. Signals that are output by the filter 106 are received by microprocessor 108 and processed to determine the mass of the mail piece 13.
The manner of determining the mass of the mail piece 13 will now be described using the embodiment of the invention illustrated in
where Fload cell is the horizontal force acting on the load cell 2, mmail is the mass of article 13, and a(t) is the acceleration rate of the article 13.
An alternate method for determining the weight of a mail piece 13 being transported across the weighing conveyer 1 is to apply a multiple frequency, time-varying velocity signal to the motor 45. The multiple frequencies may be applied, for example, by using a Fourier Series velocity profile, a linear combination of velocity components at different frequencies, to excite the mail piece 13 at frequencies that saturate the load cell 2 at each of the postal weight breaks. Such a method requires torque limiting the motor 45 to prevent inadvertent overloading of the motor 45. The motor 45 assumes an almost constant torque mode when the predetermined weight break has been exceeded. By looking at the frequencies that are attenuated by the torque limit, it is straightforward to process the load cell signals frequency spectra and determine which weight break the mail might exceed. This allows for a faster determination of the mass of mail piece 13.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US3679010 *||Aug 10, 1970||Jul 25, 1972||Tron Corp K||Digitally controlled mass flow feeder and weight integrator|
|US3805904 *||Nov 17, 1972||Apr 23, 1974||Scientech Inc||Method and apparatus adapted for high-speed weighing|
|US3834474 *||Oct 15, 1971||Sep 10, 1974||Knol W||Method and apparatus for determining the quantity of a bulk material deposited on a conveyor|
|US3917989 *||Nov 22, 1974||Nov 4, 1975||Aerojet General Co||Dual mode control of an induction electric motor|
|US4757867 *||Sep 4, 1986||Jul 19, 1988||Mima Incorporated||Single load cell weighing systems|
|US4963810 *||Oct 27, 1989||Oct 16, 1990||Archive Corporation||Variable load motor drive control|
|US5094306 *||Dec 21, 1990||Mar 10, 1992||Pitney Bowes Inc.||Apparatus for controlling the transport mechanism of a weighing scale|
|US5126647 *||Apr 17, 1990||Jun 30, 1992||Sundstrand Corporation||Pulse by pulse current limit and phase current monitor for a pulse width modulated inverter|
|US5230391 *||Apr 24, 1992||Jul 27, 1993||Ishida Scales Mfg. Co., Ltd.||Weigher-conveyor system|
|US5258579 *||Nov 16, 1991||Nov 2, 1993||Ishida Scales Mfg. Co., Ltd.||Weighing method and weighing apparatus|
|US5294756 *||May 5, 1992||Mar 15, 1994||Endress+Hauser Inc.||Conveyor belt scale apparatus|
|US5308932 *||Sep 25, 1992||May 3, 1994||Pitney Bowes Inc.||Mail processing system for verifying postage amount|
|US5393939 *||Nov 20, 1992||Feb 28, 1995||Westinghouse Electric Corp.||Apparatus and method for weighing moving objects|
|US5547034 *||Jan 10, 1994||Aug 20, 1996||Accu-Sort Systems, Inc.||Conveyor friction scale|
|US5736685 *||Nov 9, 1995||Apr 7, 1998||Ishida Co., Ltd.||Conveyor-mounted weighing apparatus|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US7687727 *||Sep 13, 2007||Mar 30, 2010||Raf Technology, Inc.||Weigh on the fly|
|US7838781 *||Feb 27, 2008||Nov 23, 2010||Motion Engineering Incorporated||System for determining the mass of an item in motion|
|US8013261 *||Aug 28, 2008||Sep 6, 2011||Elsag Datamat Spa||Method and device for determining the mass of postal articles transferred in succession along a path|
|US8063321||Feb 26, 2009||Nov 22, 2011||Precision, Inc.||Universal belt scale frame|
|US8106315||Aug 10, 2011||Jan 31, 2012||Raf Technology, Inc.||Envelope weighing apparatus with gripping compensation for variable thickness envelopes|
|US8129635||Sep 18, 2009||Mar 6, 2012||Raf Technology, Inc.||Weighing a moving object using captured torque data|
|US8153911||Sep 28, 2009||Apr 10, 2012||Raf Technology, Inc.||Dynamically weighing mail pieces in real time within an automated destination bar code sorter machine by temporarily accelerating the mail piece and capturing resulting closed loop motor torque sample data|
|US8481870||Jun 16, 2010||Jul 9, 2013||Raf Technology, Inc.||Active electronic damping for an in-line scale|
|US8481871||Aug 2, 2010||Jul 9, 2013||Raf Technology, Inc.||Dynamic thickness adaptation for an in-line scale|
|US8530762||Sep 17, 2010||Sep 10, 2013||Raf Technology, Inc.||Flatbed weigh system with vacuum capstan roller|
|US8987613||Mar 7, 2012||Mar 24, 2015||Raf Technology, Inc.||Automated weighing and franking mail pieces at transport speed|
|US9018544||May 16, 2012||Apr 28, 2015||Raf Technology, Inc.||In-line conveyor scale with a primary first motor to provide constant torque, a secondary servo motor to provide fine-grained variable torque in response to a closed loop torque sensor, and a processor to assertain weight of an item conveved based on the closed loop servo motor response|
|US9091585||Apr 12, 2013||Jul 28, 2015||Raf Technology, Inc.||Smart phone scale that uses the built-in barometric pressure sensor or orientation sensors to calculate weight|
|US20110011649 *||Mar 16, 2010||Jan 20, 2011||Kabushiki Kaisha Toshiba||Weight detection apparatus|
|U.S. Classification||177/1, 705/407, 177/25.15|
|International Classification||G07B17/00, G01G19/00, G01G9/00, G01G19/22|
|Cooperative Classification||G01G19/005, G07B2017/00701|
|Apr 7, 2011||FPAY||Fee payment|
Year of fee payment: 4
|Jul 2, 2015||REMI||Maintenance fee reminder mailed|